Load centers and other electrical distribution devices are commonly used in residential, commercial, and industrial applications. Individual circuit interrupters are mounted within these devices to protect branch circuits against overload and fault conditions. Basically, circuit interrupters like circuit breakers and fusible switches comprise a pair of separable contacts, a spring-operated mechanism for effecting separation of the contacts, and a tripping mechanism or fuse which automatically releases the operating mechanism upon occurrence of an overload or fault condition.
Load centers provide an enclosure for an interior assembly including several components for receiving electrical service and distributing the service to branch circuits. The interior assembly usually includes a panel constructed with bus bars or projecting lugs to form disconnect contacts for the removable individual circuit breakers. These bus bars and lugs are rigidly attached to the upper surface of the panel support molding. The panel incorporates an insulating base to carry an incoming line terminal for each phase to a main breaker. The main breaker is aligned with a neutral base and lug barrier base to provide for electrical connections between terminals or lugs located on the bases. The circuit for each phase is completed through the individual circuit breaker and terminals on the neutral base.
The main breaker usually incorporates line and load terminals designed to accept copper or aluminum stranded wire. In most installations the electrical service enters the load center enclosure from either the top and bottom wall. When the service feeds the interior assembly through the top wall of the enclosure, the "ON" terminals of the main breaker are connected to the field installed stranded wiring and the "OFF" terminals are connected to the bus bars of the panel. When the service feeds the interior assembly through the bottom wall of the enclosure, the "OFF" terminals of the main breaker are connected to the field installed stranded wiring and the "ON" terminals are connected to the bus bars of the panel. The connection to the bus bars of the panel is usually made with a solid copper or aluminum connector bar. The breaker is modified to include a stud or bolt to fasten the connector bar to the breaker. Most terminals on main breakers are designed for connecting to stranded wire and not a solid connector. A problem can arise in providing proper electrical contact between the terminal and a solid connector during both normal and shorting conditions of the main breaker. Connection to the solid connector should be made without deforming or otherwise damaging the terminal. To provide the flexibility of either a top or bottom installation of service, there is a need for a solid connector which can connect to the terminals of the main breaker without diminishing electrical contact or deforming the terminal.
Each of the components of the interior assembly must be in proper position relative to one another to complete the electrical connections. The interior assembly must also be mounted in the proper position within the load center enclosure itself. Problems arise in providing the required alignment between the components of the interior assembly and within the load center enclosure. The need arises to align and mount an interior assembly in a load center enclosure which often provides limited space with little room for maneuvering.
Other problems caused by aligning and assembling the load center interior is the quantity of parts that must be tracked, inventoried, and supplied in the field to properly complete the assembly. A reduced part count, avoiding the use of complicated tools, and less manual labor during assembly would decrease installation time and cost.
Mounting the interior assembly within the load center has commonly used a plurality of fasteners like screws and bolts protruding through the rear wall of the enclosure. A variety of different hole patterns are normally provided in a single enclosure to provide flexibility in mounting more than one type of interior assembly. Accordingly, not all of the holes may be used to mount a particular interior assembly. In certain applications it is undesirable to have holes in the enclosure. Moisture, rain, or other hazardous materials may leak into the enclosure and create a dangerous condition. The need arises in certain applications for an interior assembly which can be mounted within a load center enclosure without creating holes in the walls of the enclosure.